Single WDM channel efficient wavelength shifting and/or amplification using counterpropagating optical parametric amplifiers

We theoretically and numerically study the difference frequency generation and the signal amplification bandwidth together with the pump wavelength acceptance for counterpropagating optical parametric amplifiers. It is shown that the specific advantage of those amplifiers is that the DFG and amplification bandwidth is much narrower than in a co-propagating scheme, thus making it possible to shift spectrally or to amplify selectively a single channel over the several present in WDM optical fiber communications. Moreover, the pump wavelength acceptance is shown to be as broad as in the co-propagating scheme. The implementation of such counterpropagating optical parametric amplifiers in a quasi-phase-matched LiNbO3 waveguide is discussed.